1. Field of Invention
This invention relates to an image reproduction apparatus that can operate in a simplex, or one-sided, reproduction mode and a duplex, or two-sided, reproduction mode. More particularly, this invention relates to handling the feed path of the original document to control output of the original document.
2. Description of Related Art
To accomplish duplex copying, it is generally necessary to invert the original document to effect reproduction of both sides of the document. Inversion adds time to each copy job and generally requires a longer feed path with additional hardware elements to invert the document and control the elements in the assembly.
Duplex copying can reproduce both sides of an original document, either on a single sheet (two-sided reproduction) or on two different sheets (one-sided reproduction). With either type of reproduction, it is desirable to output the original document and the reproduced pages in the same order and orientation as the original input documents. When original documents are inverted during reproduction, it has been necesary to pass the original document sheets back through the feed path to output the sheets to face the same direction and be in the same page order as when input.
In Many conventional duplex reproduction devices, the original document is fed through an extended feed path in which one side of the original document is reproduced and then the original document is flipped over and returned to an original supply tray for reproduction of the other side. During the second pass the document is again inverted and output. One such example is shown in U.S. Pat. No. 4,125,325 to Batchelor et al. that uses a deflector to direct sheets bearing a reproduced image facing a first direction to a return transport that delivers the reproduced sheets facing a second, opposite direction to an auxiliary supply tray for duplex copying. However, such an extended feed path requires additional space within the device and time to transport the copied sheets to the auxiliary supply for refeeding.
Other reproduction devices use, what is commonly termed, an inverter. An inverter effectively reverses the sheet orientation in its direction of motion. In other words, the lead edge and the trail edge orientation of the sheet is reversed. Depending on the location and orientation of the inverter, such reversal may also cause the sheet to be inverted (turned over). Generally, an inverter is associated with a sheet by-pass path and gate so that a sheet may selectively enter or by-pass the inverter, thus providing a choice between inversion and non-inversion. Inverters are very useful in many different reproduction applications, but suffer from reliability problems.
An example of an inverter for use in a recirculating document handler is U.S. Pat. No. 4,553,828 to Burger et al. that uses an inverting roller to selectively invert or not invert a sheet as it is fed back to a bottom feed supply tray. For duplex copying when the sheets are finally stacked, they are each inverted from their original orientation.
Another example is U.S. Pat. No. 4,384,782 to Acquaviva in which documents are top fed in 1-N order from a supply to a feed loop that selectively inverts the documents prior to reproduction and then restacks the originals from the bottom of the supply.
There are various known ways to control duplex reproduction. For example, in U.S. Pat. No. 4,278,344 to Sahay an inverter is actuated only during single document circulation and is inhibited during successions of contiguous plural document copying circulations. Thus opposite sides of the documents are copied in alternate successions. In U.S. Pat. No. 4,355,880 to Stemmle, copying documents in serial page order is accomplished by circulating the documents in a first and last circulation through a non-inverting reversing document path between the stack and the imaging station. Some devices, such as U.S. Pat. No. 4,468,114 to Pels et al., adjust the circulation based on the particular copy job for increased efficiency.
Additional circulation such as in the above devices to effect proper document orientation, however, adds time and increases energy consumption and thus adversely impacts efficiency and general wear on the reproduction machines. Reproduction devices must provide reliability and are generally required to have the ability to operate at high speed. It is also often desirable to provide compatible circulation of simplex and duplex documents in the same document handler.